Method of and apparatus for



H. K. HlTCHCOCK.

D N A G N D N. Dn G 0 .i IL A on CL T A M D LL D IM WS DN YA LH EC Nc..rrM G MN WH LTI DIO P0 AM RS 0 rr S .U .l A un, A F P. A D N F 0 D. 0 unT E M APPLICATION H n '.9. l. 1,311,519.- LE "UG -`95 memdJuly 29, 1919.

4 SHEETS-SHIRT l.

A A venten @v @wf ITNES'SES A r l H.. K. HITCHCOCK. APPLYING FINELYDwmED M SMOOIHING MEcHANIsM. APPLICATION FILED AUG.9.I9I5

FIB.

mam To @BINDING AND Patented July 29, 1919.

4 SHEETS-SI1LT 2.

METHOD 0F AND APPARATUS FOR WITNESSES fewwf /5 @7 M www . H. K,HITCHCGCK. METHOD 0F AND APPARATUS Fon APPLYING HNELY olvlDEo MMERIAL T0GRINDING AND SMOOYHING MECHA'NISM. APPLICATION FILED AUG.9 l9l5 l 1,311,51 9, Patented July 29, 19N). v 4 SHEETSkSHtLT 3.v

FIEB.

WITNESSES 'y @im www;

To all whom it may (fonce/11n: A futliel 013;? eet o the 'inventl in' Eeit known that i., iALBnn'i h. HITGH- fide e metlied :wd

(001,' e resident of Fit'tsom'gli, in die county lense mixtuie elf eneees) of Allegheny :md 'State of Pennsylvanie, ivieuitl, especially efthe li have invented e new and useful improveeui'ecl by eliminating fromt l nient in Metliofls of and Apparatus for Apin the grading vessei'elle euvel-liuc. i

'plying' i `iiieljvl iv-iled Materiel to Grinding but ieteining in seidYeeee. tre ebi'e and Smooth.. Mechanism, of which the teriel et saidlevels, se :is te meint' following is speeiieetion. cient supply of theinei grade@ 'in This invention i'eletes to method and ap- Sion in a.Single 'f .esel Without paiu'tus for handling7 grading and applying ofCollecting anal. settling mem in a e finely divided abrasive material togrinding Vessel, thereby securing more i'epill nmehineS; Such Send orotliei abra-cling eient opel'eti'on of the appar: i

material to apparatus for grintling or iinisliing, and enenling; theigrmisiiing plete glass. ing operations to eea-fiel ou The inventien relates'to that class of nomically, witl'i less leni, l 7e*- znetiiode andapparatus im* grading' elurw the materiel, in e, elio sites and applyingthe same to giinding m11- simple an eppeietus pos (shines wherein finelydivided abrasive ma fin'tlier ebjeet of tml 2e teifie., cli es; sami.)ySepsinrz'iiwtl into gymles pivot' e, method mi To* ei iiiliereni;einzel,- Wliile in suspension in e -clenee niixtuye o" the liquid .eueiies tleeclilied iii my iletent No. peniled in e iiquifl 'QBAM,iepten'iliei 21,1909, and which tained the grading abrasive niziteiielwhile in suspension in elle grades being uiiifeimljf o e liquid iscirculet (l lepeeteclly from the rions levels in eeifl ve l, So tetgrading vessel te the grinding machine and utoi can always rely upm theelii beek ege' es described in my latents No. @zich gratie of arbmdingmiiteiiel 93%,"12 of September 2l, 1909, and Nos. rions ievels Vin thegrading v 21,056,415 and 17056,'i16 of Merch 3, '1913, which the densityof the Ini'zzt-me anti is an improvement upon the invention sel isConstantly 'indioatetl to the en described zu1delai1n-eclin myapplieation for that he will detect otlieiwise im; method" of applyingabrasives to grinding changes therein and een select tf machines, leilDecember 13, 1913, Seiial level fiom which to withdrew No. 806,59l.abrcaciing lneteriei of tin @ne object oftlie invention is to piovicleevery Stege of the griini e. method and apparatus wliieii pioduces inopeetien.

e si grmling zt elezuiei and more Textile? objects e aecuiate separationei Classification of the ait obv-'ions and in different grades ofbieding materiel, which detail iiei'e'iimftei e@ else pte-dunes etleneei' mixture of the abiaai'- in the grimling a' ing nmrteriel witht-lie liquid in which it ie gless, and. other euifme suspended, and inwhich the grading epe1 'tei'iei is supplied, it e eee ation is c'arzietlen under uniform coiiis highly fleeiifalle te neve th tiene., with theproduction of sharply diien plied at any one 'time ee nearly unifeini Lee5 entiziteol grades of materiel which are niaines poesible. Tbeirut-fnl effects et miteiiietl et the Vai-ione levels in 'the grading'plepely graded meteiiel ippei'ent eren. yvessel, as e consequence ofwhich contemiduring the rough oi" were@ nation of one grade by particlesfreni any which case it ii materiel is other grade is largely avoioleclthe product tlie coarse, it inte eyes with tin- 5e ie improved, entimore eiiicient resulte ai: tive grinding eetien oeceuse te theementseeuz'efi, and at ltile seme time the eppei'etus 'that it disiieceemeteiiel it i necessary for eel'rgnng out the .method is the totalgrinding eetioii., and is We simpliiieai and the space required for itsin fnl of abrasive met-wiel beeauee Snell i stelletiei ieeucetl.particles ae being reinem te e il grinding, and in any event smoothingor finishing operation.

condition Without producing any grinding elfect. But it is during thestages of finer grinding that the ettects of non-uniform grading aremost harmful, as any coarse material mixed with the finer material produoes crushes or sand holes in the surface being ground, therebynecessitating further grinding to take out such rough ground spots andgreatly delaying the tinal nishing, `or if not done the finished productis of an inferior quality.

In my prior application, Serial No. 806,594, before referred to, l havedescribed and claimed one method for overcoming .these harmful effectsby more accurate grading or classification of the material in thegrading vessel and the rapid introduction. of the coarse or unused sandor other abradsingle batch, or at least stages of the rough l completingthe introduction of the coarse abrasive material prior to Ithecompletion ofthe rough grinding or facing and the beginning otthe Theelliciency of the system described in said application has so materiallyreduced the time of' he faic'ng and finishing operations and has' soreduced the total quantity of new abrasive material'for each side ofglass that everyrpartrele of fine sand produced during the roughgrinding operation must be conserved in order'to furnish a suilicientsupply of the finer grades for the finishing operation. The finishingoperation is also more advantageously conducted when the mixing materialin a rapidly during the early y ture of abrading material with theliquid has a certain density, .which density isl greater than .thatordinarily found in any sirgle. grading apparatus.

he present invention is intended to secure the beneficial results abovespeciied and to also provide a method and apparatus whereby all oftheabrasive material, both the original supply and the used material, israded or regradedA under uniform conditions and in a manner to collectin the upper portion of the grading vessel all of the ner abradingmaterial produced during the grinding operation, which material is.-

condensed or thickened by elimination of the surplus water at variouslevels in the grading vessel, thereby enabling the grindmg and finishingoperations to be carried out with a minimum quant-ity of' abradingmaterial, but nevertheless insuring a sufii- .cient supply of the finergrades for the 'finishing operation, so that theentire operation can becarried outI more economically,

with less liquid, less handling of the mate-- rial and With vthesimplest form et appa# ratus. f

Various forms of apparatus are suitable 4for carrying out the method. Inthe accompanying' drawings, one arrangement of,

neuere suitable apparatus is shown, but it .is under-A stood that thisis merely illustrative and does not limit the invention.

In the drawings, Figure i is a plan view of the apparatus, thedehydrating cones and gutter being omitted for clearness ofillustration; 2 is an elevation thereof, the sump being shown insection;` Fig. 3 is a sectional elevation of the grading vessel taken onthe line 3 3, Fig. l, and looking in the 75 direction oi the arrows, andshowing the dehydrating cones and gutter-into which they discharge; Fig.4 is a similar section. on the line L -i, Fig. l, looking in thedirection of the arrows; Fig. 5 is a detail view of a so suitableindicating device; Fig. 6 is a detail plan view of the outlet from thegrading vessel; Fig. 7 is an elevation thereoic viewed from the insideof the ta1il ;Fig. 8 is a. sectional elevation ou the line 8-8, Figs. (iand 35 7; Fig. 9 is a plan view or" the grading vessel; and Fig. 10 is adetail sectional eleve.- tion of one of the dehydrating cones.

ln the drawings, 'l indicates the table oi one form oi' 4glassgrindingmachine pro so vided with a pair oi runners 2 of the usual form.These parts, however, are merely fypical of one form of grindingapparatus to which the invention may be applied.

The table l is surrounded by a gutter 3 e5 connecting with a crossgutter -fi which carries the liquid and used abrasive `from the tableover a screen 5 to the pit or sump 6 having the usual overiiow'tl foreliminating the excess liquid, the slimes, and the abrad- 10e ingmaterial too fine for further use, 1from which it is drawn through pipe7 by means of a 'suitable pump, such as a centrifugal pump 8 driven by asuit-able motor 9, and is forced through pipe 10 upwardly through 105the bottom oi' the grading-vessel ll, thereby `producing in said vesselan upward iiow of the liquid relative to the abrading material, andproducing a separation of the material `into grades of different sizes,depending'll vupon the ratio of the weight of the particles to theresistance to. liow otl'ered by the upward current of 'liquid, as iswell understood and as described in my Patent No. 934,441, aboveidentified. The pump S may deliver the mixture ot abrading material andliquid to the grading vessel at a level between its bottom and the upperlevel of liquid thereinJ as described `in my copending. application formethod and apparatus for 12o applying abrasive material to grinding andsmoothing mechanism, iiled August 9. 1915, Serial No. 44622, in whichcase the grading vessel will be provided with a supplemental watersupply connected thereto et a level below that at which the abradingmaterial is introduced to said vessel for producing or augmenting theupward How of the liquid relative to the downward movement of theabrading material. The particular accumulating its own particular gradeof line material and condensing it by abstracting the superfluous liquidtherefrom, so that these liner grades are collected and stored duringthe several cycles of the rough grinding loperation forlater use duringlinishing. The character and position of these Agrades can be regulatedbymeans of theI valves 24.

Provision is made for separately withdrawing the several grades from thegrador pressure in the supply of mixture to the table. As shown, thesepipes are all connected to a common casting or conducting member 29which is secured to the wall 0f the grading vessel and is provided witha plurality of inwardly projecting tubular portions, one for theattachment or' each of the withdrawal pipes. As shown, the withdrawalpipe 2G has its inner end opening near the bottom` of the grading`vessel 11, in the coarse sand Zone; the intermediate withdrawal pipe 27has its inner end opening at a poi-nt between the top and bottom off thecone, in the intermediate sand grade zone, while the withdrawal pipe 28is in the forni of a flexible hose or pipe of suiicient length to reachto the bottom and also to the top .of the grading vessel and having itsfree end vertically movable, as hereinafter described, so that it cantake the sand out of said grading vessel at any desired point. A

The several withdrawal pipes are constantly open so that water andabrasive material from each oil the several grades in which said pipesterminate is constantly discharged, t iereby further contributing to themaintifinance of a uniform pressure and uniform head in the gradingvessel. As shown, the openings through the casting 29 discharge into avessel or casing 30 secured to the outer wall of the grading vessel andprovided with an outlet conduit. 31 leading to the sump 6. Pivotallymounted adjacent to each discharge opening through the casting 29 isa'discharge pipe, which pipes are marked respectively 26a, 27a and 28,and are so mounted and have their inner ends so formed that when loweredthey fit over the respective discharge openings in the casting 29 andform a'conduit for conducting the discharge through that'particularopening to a trough 32 extending through the outer wall of the vessel oreasing 30 and leading to the spout 33 which. projects over the grindingtable l, preferably between the runners 2, and which is perforated todischarge the mixture of sand and water onto the table. The dischargepipes 26, 27

and 28a are preferably bent to substantially goose-neck form, as shown,although this is not essential; and are arranged to beswung upwardlyabout their pivots by suitable operating cords 26, 27b and 2S", each ofwhich. is knotted'so that it may be slipped into a notch in a holdingmember 34, or provided with other means whereby the pipe can be held inelevated position.

When all of the pipes are elevated the mixture discharging through eachof the withdrawal pipes 26, 27 and 28 returns through conduit 31 to thesump 6, but whennecessary during the finishing operation, its

free end is supplied with a weight for sinking the pipe. This weight isconnected by a cord or cable 40, which passes over a sheave or pulley41, to a oat Ll2 in a cylinder i3 supported at the side oi the gradingvessel 1l. Connected to the lower end of cylinder 43 is a water pipe 44which preferably extends to a point adjacent tothe front of the tablewhere it is. provided with a suitable three-way cock or valve i5 whichhas a discharge outlet and also communisetting said cock to the properposition -water may be admitted to the cylinder 43 to lift the float 42and allow the weight 39 to sink the end of the flexible hose 28, or maybe discharged from cylinder i3 andy-thus allow the ioat-42 t0 sink andelevate the end of flexible pipe 28 in the grading vessel.

Precerably, a second cable'ior cord 46 is connected to the loat 42 andpasses over pulley el and over a second ulley 47 to the opposite side ofthe tank w 1ere itoperates a suitable lindicating means, shown as aweight 88 which is preferably held at the same level as the weight 39,so that the position of weight 3S indicates the exact position of thefree open end of pipe l,23in the lgrading vessel.

Preferably, also, suitable means is provfvided for indicating to theoperator the condition vessel.

prises of the mixture within the grading The indicatinl means showncoin-- e though it may lie et any desired level. This` liydrometer isconnected by e cord 55, lever pivote( .et 57 and couuterweighted at 58,and oord 59,. to e suitable indicator, shown es au electric lamp 60arranged to move up end down in casing 6l having a plurality of Windows62 located et different levels and preferably Covered with differentcolored glasses, such es red for the upper window, white for theintermediate and green for the i window,

The ig-rsition of the hydrometer 5i depende upon the density of themixture in Zeri@ mater "seuil, 'in which Cese the indicator 60 el ndice'ion of the condition' or" i rr. :"ture, that is, its density amount ofmeterial thererdes do not affect the hydrometerf indicator also advisesthe griiiding of' 'elle Conditiouof each tuhle in e tables, that is,Whether e table is ing the rough or fee-ing; opereriier it is et *sheintermedieie grindo11, or whether it is doing .fine finishing, ByWatching? the menigte x.u the indirators ori eeeh of e series griiioirlgi .oies the foreman can tell at n nee 'whether the tables are properlysuped 'with sand es Well es the character of operation 'their iuprogress, und een so edjyust the' amount of coarse sund used et eeelifacing operation that the proper ruirf tire will be insured` le carryingouiI the method on the appar seus described the sump G und gradingAvesel il ere first filled with water and 'the u S is started tocirculate the Water. l

'he discharge pipes '26, 27 und 28 re elevated so time the liquid i`discharged zito the casing.; or vessel 30 und returns through the Si tothe sump 6. rhe pump runs continuously und at such a speed 'ther thevelocity of flow upwardly in the grading vessel is maintained uniformand also ai o sneed sufficient to vprmluce eu overiow the severaldellydretiug cones end ille overflowY pipe l2.

.sured charge of send sulieien. for "'iuding o'gieretion from lue; ismeasured into the density of the mixture end so that all of the sendgets into the circulation system before the line grinding begins. Thissend is cerried up into the grading vessel and is graded according toits size, the larger particles essuming positions neer the httom of thecome and the grades becoming iier and liner up through the conical undcylindrical portions of the vessel. All dirt, scum and mterial too finefor use flows over ito the gutter 2,

together with the cler liquid eliminated et the various levels by thedehydret-ing cones, and delivered through the outlet l2. to the gutter 3and returns to the sump Where the excess Water and slimes:ire-eliminated from the system through overflow 6, Since the coarsesend at first predominates, the mixture iii Jche hotom of the cone l isdense so that the hydrometer 5% 'rises sind moves the indicating lamp GOto e position opposite the lower window iu casing Gl zuid displaying agreen light, which menus that the system is supplied with the properquueiity of coarse sund for economically' effecting the rough grinding.

By properly manipulating the several discharge pipes 25a, 27a and 28,the several grades may he supplied 4rom the grading vessel to thegrinding table seperately zuid independently and in order and to anyextent or degree desired. During the rough grinding, pipe 26a is loweredlo supplycoerse materiel from near the 'ootom oi? the grading vesselinto the trougl'i 52 from which it flows to the spout aud is dischargedupon the table, while the discharge pipes and 28a are iii elevatedposition so that the mixture discharging 'through Withdrawal pipes 27end 28 returns to the sump 6. lVhen the whole batch or" sund. has beenintroduced into the sump und cerried to the grader the hydrometer is iuits highest position, :md as the grinding proceeds and the Course sundis reduced in size it gradually falls iis' the Saud supplied to thetable from the pipe 26 becomes liner and liner. When the roughgriudirucr mierutiou has proceeded fer enough the discharge wipe 2W islifted und the dischurg'e pipe 2i is lowered, and thereafter econsiderably finer grade of material is delivered to the table from alevel between the top and hottom of the cone, while. for the .finalfinishing; operation the pipe 27a is lifted und the pipe is lowered,thereby discharging luto toe trough :'32 umteriel comii'ig through thewithdrawal pipe 28. l

Buriug the rough grinding; some of the sund is thrown oil? the telde in.the eoudi tion in which it is received, especially during the siege ofadjusting the runners in'to full voulue-t :md full pressure with 'thefehle; The material so thrown ol the mhh* luto the gutter 3 reurns tothe sump and Duck again ino the grading vessel. During all the movedupward at a uniform rate of speed,

grinding operations some of the sand is 'broken up by the grindingaction, producing grades oi".- sznaller size, some mud and some materialtoo fine for further use. During cach cycle`of the circulationtlie mudand `material too line for -furtlier use are carried oitthrough theoverflow pipe 12,'

"open end of pipe .285 is placed in the zone of the grade with which thefinishing opera tion is to begin,.say, at the bottom on the cylindricalpoition 20 ol the vessel 11, and may then be raised at intervals by aseries of steps or jumps so as to delivei` to the grinding tab-lesuccessively portions of the f material of liner and `finer.grades,until the smoothing operation is completed. Prereiably, however, theopen end ot pipe Q8 1s traversing in turn each of the various levels inthe cylinder 2G in a series of iniperceptible changes, so that the gradeof material supplied to the table changes gradually from theintermediate grade near the top of the cone to the very finest grade atthe top of the cylinder. To secure uniform results and also to regulatethe time of grindr ing, the three-Way cock l5` is so set as to dischargethe water from the cylinder 43 at just suoli a rate that the float 42will raise the open end of pipe 2S at the proper rate `ot' speed. lfdesired, the outlet of cock 45 may be made of such a size as toconstitute the limit of the maximum rate of discharge. Thisdoes' awaywith the necessity of watching the apparatus closely during the finegrinding and adjusting the flexible pipe at proper intervals for changesin grades.

During all of tlie grinding operation,

from roughing to finishing, the abrasive inaterial is .in suspension ina liquid and isveiiculatedL repeatedly from the grading vessel to thegrndingtable, then to the sump, and baci.: to'the grading vessel; slimesand line material being separated at the sump during the course of eachcycle. After the introduction of the initial supply oi charge ofabrading material from the hopper 17 no more abrading is'introduced intothe system, but theoriginal chargev becomes finer and finer during theprogress of the grinding operation, and is collected and condensed. inthe upper portion ofthe grader to supply tlie necessary amount of linesand for the finishing.

As the grinding operation proceeds the density of the coarse mixture inthe grading vessel decreases and `the hydrometer 55 sinks, therebyraising -tlie lamp 60 and changing the indication from green to whiteand then to red, thereby indicating to the orefY man the particularstage of grinding operation.

When the grinding operation is completed all of the discharge pipes2'6", 27 and 28* are raised and the mixture is allowed to flow from thegrading tank into the vessel orcasing 30 from which it flows to thesumpv 6, thereby enabling the circulation to be continued betweensuccessive grinding operations, or during the time that the glass onlthe table is beingr changed.

y Usually, upon starting a given system a; slight excess of coarse sandis supplied with each of the first few batches, so as to insuresufiicient coarse sand for the rough grinding, and which excess isbroken up on the table to forni finer grades which ae'- cumulate in thecylindrical portion 20 of'I the grading vessel and form a reserve sup-Aply line material which can be'drawn upon in case it is necessar ordesired to nlsh or renish a side o glass without first going through thegrinding operation. After a sufficient excess of fine sand hasaccumulated in' the 'vessel 11 the measured batches of sand thereafterintroduced are calculated so as to-be vjust suliicient for one completegrinding operation. The mudy and fine material washed outl through theoverflow during each grinding operation are equal viii quantity to thenew batch of sand supplied to the system for each grinding operation. Byoperating the system in' this manner each batch of sand introduced intothe system is graded and suppliedto the table under conditions identicalwithl those in the preceding operation, and these conditions aremaintained dui-ng the entire course of each and every grindingoperation.

The method of grading abrading materiel in a vessel, conducting thematerial from the grading vessel to the` grinding mechanism, and varyingvthe grade ofmaterial conducted to the grinding' mechanism byimperceptible changes` is not claimed 'herein but is claimed in myapplication Serial No. 806,594-, filed December 13, 1913.

`What l claim is zl. The method described. consisting in separatingabrading material mixedwith a liquid in a vessel into different grades,eliminating,r surplus liquid from various levels in said vessel, andwithdrawing said grades and conducting the same to grinding mechanism.

2. The method described, consisting vin separating abiading materialmixed with.

a liquid in a vessel into different grades, condensing several grades insaid vessel, and withdrawing said grades and conducting the same togrinding mechanism,

3. The method described, consisting in nism, a grading vessel, means forproducing.

in said vessel an upward flow or travel of rao tb liquid relative to thematerial to separate the material into grades, means for conductingdifferent grades independently from said vessel to the grindingmechanism, and a plurality of outlets at dill'erent levels in the upperportion of said vessel for withdrawing liquidI from said levels tocondense the various grades in the upper portionv'of said vessel.

16. Apparatus of the character described, comprising in combination,grinding mechanism, a grading vessel, means for producing in said vesselan upward iow or travel of the liquid relative to the materialtoseparate the material into grades, means for c'onducting said gradesindependentlyv from said vessel to the grinding mechanism, and aplurality of cones having their open lower ends located at dillerentlevels vin said vessel,

for,` withdrawing superfluous liquid from said levels while retainingand condensing the various grades in said vessel.

17. Apparatus of the character described, comprising in combination,grinding mechamsm, a grading vessel, means for producing said yvessel anupward ow or travel ot' the liquid relative to the material to separatethe material. into grades, means for conducting` dilerent gradesindependently from said vessel to the grinding mechanism, means forreturning saidl material in suspension 4in a liquid from the grindingmechanism to said vessel and introducing the same thereinto, and aplurality of `cones at different levels' in said vessel for withdrawingsuperluous liquid from said levels while retaining and condensing the,Avarious grades infs'aid vessel. 7",

`18. The herein described method which consistsA in gradingabradingfmaterial in a vessel while in suspension in a liquid to causethe grades to assume different levels, withdrawing some of the grade-swhile in suspension in the liquid from said grading vessel andconducting the same to grinding Imechanism while lea-ving other gradesin said vessel, and varying the grades so conducted ,to the'I grindingmechanism by imperceptible changes.

19; The herein described method which consists in gradingabradingmaterial in a vessel while in suspension in a liquid to cause the gradesto assume didere'ntlevels,

'withdrawing said material while in suspension in the liquid from saidvessel and conducting the same to grinding mechanism, returning thesame' while still mixed with ylunatic progressively and by imperceptiblechanges.

20. Apparatus of the character described comprising, 1n combination,grinding mechanism, a grading vessel, means for grading 1 abradingmaterial in said vessel while in suspension in a liquid to cause thegrades to assume different levels, and means for conducting the materialin suspension in 'the liquid from the grading vessel to theV grindingmechanism arranged to automatically and uniformly vary the grade ofmaterial conducted to said mechanism.

' `mpi/apparatus of the character described comprising, in combination,grinding mechanism, a grading vessel, means for grading abradingmaterial in said vessel while in suspension in a liquid to cause thegrades to assume dilerent levels, a flexible pipe lying within thegrading vessel for withdrawing the mixture from said vessel, andautomatic means for progressively moving the open end of said pipeupward through the mixture in said vessel to thereby progressively varythe grade of material conducted to the grinding mechanism.

22. Apparatus of the character described comprising, in combination,grinding mechanism, a grading vessel, means for grading abradingmaterial in'fsaid vessel while in suspension in a liquid. to 'cause thegrades to assume 'dililerent' levels, a flexible pipe lying within thegrading vessel, lor withdrawing the mixture from said vessel, automaticmeans for progressively moving the open end of said pipe upward throughthe mixture in said vessel to thereby progressively vary the grade ofmaterial conducted to the grinding mechanism, and means for indicatingthe position of the open end of said pipe in the grading vessel.

23. Apparatus oi the character described comprising, in combination,grinding mechanism, a grading vessel, means for grading abradingmaterial in said vessel while in suspension in a liquid to cause thegrades to assume different levels, a flexible pipe lying within thegrading vessel for withdrawing the mixture from said vessel, a reservoirfor liquid, a float in said reservoir, connections between said lioatand the open end of said lill) Miti lll)

llt

flexible pipe for elevating the latter, and means for withdrawing liquidfrom saidV reservoir to elevate the inner open end of said pipe.

' 24. Apparatus of the character described comprising, in combination,grinding mechanism, a grading vessel, means for grading.

abrading .material in said vessel while in 13o suspension in a liquid tocause the grades tov assume different levels, a iiexible'pipe'lying`within the grading vesselfor withdrawing thevmixture from said vessel, areservoir foru. liquid, ya oat 1n said reservo1r,'connect1ons betweensaid float and the'open end of said flexible pipe forelevating the'latter, means for withdrawing'li'quid fromr said reservoir to elevatethe inner open end of said pipe, 'and an indicator vertically movable,with said pipe to indicate the level vof the latter in said vesseLg A25.Apparatus'of fcmprirsing, in combination, grinding mechanism, a lgradingvessel, -means for grading abrading material in said vessel 'while insuspension in a liquid to cause the grades to assume diierent levels, aflexible pipe lying A within the .'gradingvessel for withdrawing themixture from said vessel, a reservoir for liquid, a float 1n saidreservoir, yvariaivle means for withdrawing' liquid,A from .sald

Ireservoir, and connections bet/Ween said float and the open end of saidflexible pipe for elevating thelatter. I w v Q6. Apparatus ofthecharacter described comprising, in combination, grinding mechanism, agrading vessel, means for grading abradin material inl said vessel whilein suspension in a liquid to cause the grades'fto assume diierentlevels'iay flexible pipe ,ling

lthe 4character described.-

within liegradi/ng vessel for withdrawing the mix ure from said vessel,a reservoir for l1quida float 1n said reservoir, variable means forwlthdrawmg liquid from saidreservoir, connections between said ioat andthe open' end of said flexible pipe for elevating the? latter,l and anindicator vertically movableon the outside of the grading Vessel andarranged to rise and fall in unison with said pipeto thereby indicateitsposition in the grading vessel.

27'. Apparatus oi the character described comprising, incombination,grinding mechap nism, a grading vessel, means for gradingabradingmaterial in said vessel while in suspension in a liquid to causethe grades to assume different levels, a iieXible pipe lying withinthegrading vessel for withdrawing the mixture from said vessel, means formoving the Lopen end of said pipe upwardly through the mixture in thevessel to progressiyely varythe grade of material. conductedtothegrinding mechanism, and an indicator

